In recent years a new type of ceramic heater roller, as disclosed in U.S. Pat. No. 5,616,263, has been developed for use instead of steam-heated, oil-heated and induction-heated rollers in the papermaking, printing, and the paper, film, and foil converting industries. Such rollers have been used as web heating rollers, drying rollers and drums, laminating rollers, embossing rollers, and cast film extrusion rollers.
These rollers operate in machines in which electrical connections must be made to the roller. In a prior published PCT patent document WO 96/31088, based on a prior U.S. application Ser. No. 08/414,430, an electrical contact assembly used a metal contact which directly contacted a conductive layer that extended down a tapered end of the roller. The end of the roller included a double bevel or double taper construction, a first O-ring which was located above the contact region, and a second O-ring which was located below the contact region, to seal the contact region against contaminants and fouling due to the formation of oxides.
The prior construction required contact pressure, and precise alignment and fit between the contact and the band on the roller. The O-rings also required some careful handling during assembly for proper fit and operation. The entire assembly had numerous parts which involved cost in manufacture and assembly. The prior construction also used the "double bevel" form of tapered roller ends, which are more difficult to manufacture and maintain against cracks in the ceramic layers of the roller than a single bevel construction.
The present invention is directed to improved constructions of electrical contact assemblies for use with ceramic heater rollers.